Antioxidants for mineral oil lubricants and compositions containing the same



Patented Sept. 12, 1950 an'rroxmm'rs Foa MINERAL on. Lunarcams ANDcomosrrrons con'rnmmc.

THE ssME Herschel-G. Smith, Wallingford, and my L. Cantrell, Lansdowne,Pa., asaignors to Gulf Oil Corporation, Pittsburgh, Pa., a corporationof Pennsylvania No Drawing. Application October 17, 1949, Serial No.121.902

14 Claims.

This invention relates to antioxidants for mineral oil lubricants andcompositions containing the same, and more particularly, it relates toadditional agents for mineral oil lubrl cants which inhibit theoxidative deterioration of said lubricants.

In the lubrication of internal combustion engines of all types,particularly when severe operating conditions are encountered, plainmineral lubricating oils often prove unsatisfactory in service becauseof the oxidative deterioration of the oil, with the attendant depositionon the engine surfaces of varnish, gum or sludge. Ltthermore, manylubricating oil compositions which may be highly satisfactory for thelubrication of other mechanisms have been found wholly unsuitable foruse as turbine oils.

The formation of varnishes, gums and sludges on engine surfaces is dueat least in part to oxidation effects on mineral lubricating oils. Inturbine oils the problem of oxidation is further aggravated, because innormal use turbine oils rapidly become contaminated with water.

It is an object of this invention, therefore, to provide an additionagent for mineral oil lubricants which will inhibit the oxidativedeteriora= tion of such lubricants.

It is further an object of this invention to provide mineral oillubricant compositions which are remarkably stable against oxidationunder service conditions.

These and other objects are accomplished by the present inventionwherein an addition agent for mineral oil lubricants is prepared bycondensing triphenylguanidine, N-dimethylaniline and formaldehyde in thepresence of an activated clay as a catalyst, and recovering thecondensation product. The condensation product so obtained is alight-colored product which, when added to mineral oil lubricants,confers a remarkable stability against deterioration by oxidation. Suchcondensation products and mineral oil lubricant compositions containingthem are believed to benovel and are considered parts of our invention.Contrary to what may be expected from the nature of the reactants, we donot obtain highly-condensed, insoluble resinous products. On thecontrary, when the above reactants are condensed in accorance with ourinvention, there are obtained light-colored condensation products whichare nonresinous and which are readily soluble in mineral oils.

In performing the condensation the reactants are mixed and heated to amaximum temperature of 350 F. We have found that if the temperature of350 F. is exceeded to any substantial extent, the condensation productformed tends to be resinous and insoluble. In general, the pre- 2 ierredtemperature for the'condensation ranges from to 300 F.

The proportions of the reactants may vary over a relatively wide range.For each mol of triphenylguanidine, N-dimethylaniline is employed in anamount of from 4 to 9 mols, and the formaldehyde is employed in anamount from 4 to 9 mols. Ordinarily, it is preferred to use from 5 to 10per cent by weight of the activated clay catalyst, based on the'totalweight ,of the reactants. I-Iowever, smaller amounts, as low as 1rpercent by weight, and larger amounts, as high as 20 per cent by weight,may also be employed; but larger amounts than about 10 per cent byweight are ordinarily not necessary.

Either alpha-triphenylguanidine,

/ NHCoH-s CsHiN=C OoNa or beta-triphenylguanidine,

NHCBHS- HN=0 CoHB CaH's or mixtures of the two are used to producesuccessful antioxidants in accordance with our invention.

In lieu of formaldehyde any formaldehydeyielding compound, such asparaformaldehyde, dioxymethylene and trioxymethylene may be employed. Insuch case, the amount of formaldehyde-yielding compound used is based onthe equivalent number of mols of formaldehyde yielded within the rangeof proportions of formaldehyde set forth hereinabove. Accordingly, asused in the appended claims, the term .formaldehyde" is intended toinclude formaldehyde-yielding compounds as well as formaldehyde itself.

Various activated clays are employed as catalysts in accordance with ourinvention. Such materials are well known in the art and comprise anatural clay, such as bentonite, montmorillonite, fuller's earth,floridin and smectite, which has been acid treated in order to activatethe clay. These materials are described in U. S. Patent 1,898,165, forexample.

In preparing our new addition agents, the reactants and catalysts areplaced-into a reaction vessel which is then closed and the mixtureheated with agit tlon under reflux until all of the formaldehyd orformaldehyde-yielding compound has been consumed. At this time the waterwhich is formed as a result of the condensation is removed, preferablyunder vacuum, and the dehydrated condensation product is then 3 filteredto remove the activated clay catalyst. In some instances, it isdesirable to prepare our new addition agent in a concentrate in amineral lubricating oil which may then be diluted down with additionaloil to the concentration desired in the final lubricating composition.In such instances; the mineral lubricating oil may be added in asuitable amount, say in a weight equal to the weightof reactants, to thereaction mixture in the reaction vessel, and the condensation productobtained will then be. a concentrated solution of the addition agent inthe mineral lubricatingoil.

The condensation products obtained inaccordance with our invention areliquids or crystalline solids. While the exact nature of the chemicalcomposition of the condensation products is unknown, all of the threereactants enter into a final unitary product, as has beenestablished byinfrared spectroscopy. The exact nature of the manner in which thecatalyst influences the reaction is unknown. However, regardless of anytheory involved, the, use of an activated clay catalyst is an essentialfeature of our invention, -since-if the catalyst is omitted, black,insoluble,

asaasia Example I.--Into an enamel-lined reaction vessel were charged144 pounds of triphenylguanidine (E. K. 00., Pract., M. P. 13'l142 C.)($5 pound moi) 544 pounds of N-dimethylaniline (4.5 pound mols), and 365pounds of a 3'7 per cent by weight aqueous formaldehyde solution (4.5pound mols of anhydrous formaldehyde) along with 70 pounds of Fiitrolclay (activated montmoriilonite) as a catalyst. The mixture was refluxedand agitated at 212 F. for a period of 3 hours, and then all water, boththat added with the formaldehyde and formed with the reaction, wasdistilled off. The product was then filtered through Celite and had thefollowing properties:

Specific gravity, /60 F 1.0528 Color, NP 3.25 Neutralization No 0.36

Example IL-Into an iron reaction vessel were charged 1 mol oftriphenylguanidine (E. K. (70., Pract), 9 mols of N-dimethylaniline, 9mols of formaldehyde and 10 per cent by weight of Filtrol as a.catalyst. The mixture was refluxed and agitated at 212 F. for 3 hours,and then the temperature was raised to 280 F. and all water, both thatadded. with the formaldehyde and formed with the reaction, was distilledoil. The product was then filtered and had the folv lowing properties:

Specific gravity, 60?/60 F 1.0615 Color, NPA 3.5 Neutralization No 0.25

Specific gravity, 60/60 F 1.0678 Color, NPA 3.0 Neutralization No 0.27

The condensation products obtained in accordance with the abovedisclosure from triphenyliii I -4 guanidine, N-dimethylaniline andformaldehyde in the. presence of 'an activated clay catalysts areexcellent addition agents vfor mineral oil lubricants. They are readilysoluble in all types of mineral oils, that is, parafiinic, naphthenic ormixed base mineral oils in high proportions to form concentratedsolutions thereof, which may a then be diluted down to the proportionsdesiredin the final mineral oil lubricant composition. As has beenstated, our new addition agents are remarkably effective in inhibitingthe oxidative deterioration-of mineral oil lubricant compositions. Forthis purpose small amounts of our new addition agents are generallysufllcient. For example, our addition agents may be added to minerallubricating oils in minor amounts, say from 0.001 to l per cent byweight of the mineral oil, suillclent to inhibit the oxidativedeterioration of the oil. Larger amounts of. our new addition agents maybe used if desired, but it is ordinarily unnecessary to do so.

The following examples illustrate the remarkable antioxidant effects iof our new addition agents. In the following examples, the base oil andthe same oil blended with our new addition agents are subjected to astandard oxidation test which measuresthe stability of the oils tooxidation. The oxidation test referred to is a standard test designatedASTM D943-4'lT. Briefly, the test comprises subjecting the 011 sample tooxygen at a temperature of C. (203 F.) in the presence of water and aniron-copper catalyst, and determining the time required to build up aneutralization number of 2. The flow of oxygen is maintained at 3 litersper hour. The remarkably efiective stability to oxidation of mineral oillubricant compositions containing our new addition agents is illustratedby the results shown in the following examples. H

Example IV.T0 a steam turbine oil having a viscosity of 150 SUS at F.there was added 0.5 per cent by weight of an addition agent preparedaccording to Example I. The base oil and the oil blended with theantioxidant were then ExampleV-J'o a motor oil which had been highlyrefined by aluminum chloride treatment there was added 0.5 per cent byweight of an antioxidant prepared according to Example II.

.A comparison of the base oil and improved oil follows The aboveexamples show the remarkable oxidation stability imparted to mineral oillubricant compositions by the use of our new addition agents. Mineraloil lubricant compositions containing our new addition agent aretherefore eminently suited for use where the operating conditions areextremely severe, as in Diesel, tank and truck engines, and in thelubrication of steam turbines.

The remarkable effects of our new addition agent cannot be readilyaccounted for and cannot be predicted from the nature of the reactants.Thus, condensation products prepared from other functionally similarcompounds have been found to be either prooxidant or to show noantioxidant effects whatsoever. For example, we have prepared acondensation product similar to our new addition agent by substitutinganiline for dimethylaniline. The resulting condensation product wasfound to be entirely unsuitable for inhibiting the oxidativedeterioration of mineral oil lubricant compositions.

Other known addition agents may be incorporated into the lubricantcompositions prepared in accordance with our invention. For example,pour point depressants, extreme-pressure agents, viscosity indeximprovers and the like may be added. While we have shown in the examplesthe preparation of compounded lubricatingoils, our invention is notlimited thereto but comper mol of triphenylguanidine, said productbeprises all mineral oil lubricant compositions containin our newaddition agents, such as greases and the like.

Resort may be had to such modifications andvariations as fall within thespirit of the invention and the scope of the appended claims.

We claim: 1. The process of preparing an addition agent for mineral oillubricants which comprises heat- I ing triphenylguanidine with from 4 to9 mols of N-dimethylaniline and 4 to 9 mols of formaldehyde per mol oftriphenylguanidine in the presence of an activated clay catalyst at atemperareactants of an activated clay catalyst at a tem perature of from150 to 300 F. to condense together the three reactants, and recoveringthe condensation product.

3. The process of preparing an addition agent for mineral oil lubricantswhich comprises adding an activated clay catalyst, triphenylguanidinewith from 4 to 9 mols of N-dimethylaniline and 4 to 9 mols offormaldehyde per mol of triphenylguanidine to a mineral lubricating oil,heating the mixture to a temperature not in excess of 350 F. to form acondensation product, and recovering a solution of the condensationproduct in the mineral lubricating oil.

4. The process of preparing an addition agent for mineral oil lubricantswhich comprises heating obtained by the process of claim 1.

7. A non-resinous condensation product of 1 mol of triphenylguanidine, 9mols of N-dimethylaniline and 9 mols of formaldehyde, said product beingobtained by the rocess of claim 4.

8. A non-resinous condensation product of 1 mol of triphenylguanidinewith 4 mols of N-dimethylaniline and 4 mols of formaldehyde, saidproduct being obtained by the process of claim 5.

9. A lubricant composition comprising a major amount of a minerallubricating oil, and a minor amount, suflicient to inhibit the oxidativedeterioration of said oil of a non-resinous condensation product oftriphenylguanidine with from 4 to 9 mols of N-dimethylaniline and 4 to 9mols of formaldehyde per mol of triphenylguanidine,

said product being obtained by the process of claim 1. I

10. A lubricant composition comprising a majoramount of a minerallubricating oil, and a minor amount, from 0.001 to 1.0 per cent byweight of said oil, of a non-resinous condensation product oftriphenylguanidine with from 4 to 9 mols of N-dimethylaniline and 4 to 9mols of formaldehyde per mol of triphenylguanidine,

.said product being obtained by the process of claim 1. I r

11. A lubricant composition comprising a major amount of a minerallubricating oil,.and a, minor amount, sufficient to inhibit theoxidative deterioration of said oil of a non-resinous condensationproduct of 1 mol, of triphenyl-.

guanidine, 9 mols of N-dimethylaniline and 9 mols of formaldehyde, saidproduct being obtained by the process of claim 4. v

12. A lubricant composition comprising a major amount of a minerallubricating oil, and a minor amount, suflicient to inhibit the oxidativedeterioration of said oil of a non-resinous condensation product of 1mol of triphenylguanidine, 4 mols of N-diinethylaniiine and 4 mols offormaldehyde, said product being obtained by the process of claim 5.

13. The composition of claim 11, wherein said condensation product ispresent in an amount of 0.5 per cent by weight.

14. The composition of claim 12, wherein said condensation product ispresent in an amount of 0.5 per cent by weight.

HERSCI-IEL G. SMITH. TROY L. CANTRELL.

REFERENCES CITED The following references are of record in the file ofthis patent:

Chemical Abstracts, vol. 31 (1937), page 1811. Smith et -al., J. Chem.Soc. (London), 1934, Pages 1136-1140.

1. THE PROCESS OF PREPARING AN ADDITION AGENT FOR MINERAL OIL LUBRICANTSWHICH COMPRISES HEATING TRIPHENYLGUANIDINE WITH FROM 4 TO 9 MOLS OF OFFORMALDEHYDE PER MOL OF TRIPHENYLGUANIDINE IN THE PRESENCE OF ANACTIVATED CLAY CATALYST AT A TEMPERATURE NOT IN EXCESS OF 350*F. TOCONDENSE TOGETHER THE THREE REACTANTS, AND RECOVERING THE CONDENSATIONPRODUCT.